The invention relates to a method for testing the stability of vertically anchored masts in which the mast above its anchoring is loaded with an increasing bending force proceeding from a defined initial value until at the most a maximum, predetermined test force and at the same time is laterally deflected and in which the mast after completion of the loading procedure is again unloaded and with this is subjected to a restoring force reducing to zero.
In EP0 638 794 A1 there is described a method for testing the solidity and bending resistance of a vertically anchored mast with which the mast likewise is subjected to a variable bending moment in that it is loaded with a force introduced above its anchoring and increasing in the course of the testing procedure, the measured value and the course of the force being used to determine the solidity of the mast. The mentioned force as well as also the distance about which the mast is laterally deflected at a selected location on account of the bending moment are measured simultaneously with sensors.
A linear dependency of the measured distance on the introduced force is evaluated as information of a mast deflection lying in the region of elastic deformation, whilst the determining of a non-linear dependency of the values measured by the sensors are evaluated as information of a plastic deformation and/or for a non-stable anchoring of the mast which is then recognized as not having bending resistance or is not stable and the testing procedure is stopped by unloading the mast. Thus with this method no safety precautions are to be made for the case that is not to be exected, specifically that the mast with this testing step may buckle or break. Moreover the testing procedure is only broken off by unloading the mast when a predetermined nominal value of the bending moment is achieved in the elastic region of deformation, which means that the mast is sufficiently stable and has bending resistance and does not need to be exchanged for another.
In accordance with one embodiment, the following results and information were achieved:
With this method it is not possible to determine whether the mast tested in each case, in spite of deformation lying in the elastic region until reaching the testing load, is damaged by a fracture or by a corrosion region possibly going through the mast, so that in the case of such damage one may possibly arrive at an erroneous evaluation of the remaining stability of the mast, since for example with the application of this method a linear course of the function S=f(F), wherein F is the introduced force and S the lateral deflection of the mast, or a changing bending angle of the mast may give the delusion that the mast is not damaged.
This problem is solved by the method described in the Utility Model DE 296 07 045 U in which by way of a force unit the mast above its anchoring in the same plane of testing is loaded from the side, after one another with a compression force and with a tensile force, thus with oppositely directed bending moments so that for both cases of loading there results two functions fx and fy and these can be processed in an evaluation unit and compared. Furthermore these functions are usefully displayed on a monitor and/or graphically represented with a printer for the simultaneous assessment or subsequent evaluation.
These functions with an assumed straight course particularly give much information inasmuch as they give information whether there is damage caused for example by a fracture in the mast and where this damage is located.
If both functions fx, fy have the same course and thus the same gradient, it may be concluded that in any case no damage of the mast in the vertical testing plane and in the mast region directly next to this plane will be present. If on the other hand the courses of the two functions fx, fy related to the same zero point diverge and thus have differing gradients then a mast damage may be concluded even when the characteristic curves obtained from the two functions run linearly or straight, since a mast for example damaged with a fracture even after a further development of the fracture with an increasing loading of the mast will continue to behave elastically and a fracture formation at the most would result in a small kink in the otherwise continued linearly running characteristic curve.
As has already been mentioned, from the two functions obtained in the same testing plane and from their courses also the location of the damage may be concluded. If specifically e.g. the function fx evaluated with the compression procedure has a larger gradient than the function fy determined with the tensile procedure, this would mean that the fracture is located on the side of the mast on which the tensile force is indroduced, since it is to be expected that the mast on account of the smaller spreading of a transversly running fracture, without this at the same time having to become larger, will behave more elastically than with a compression force introduced in the opposite direction with which oppositely lying fracture surfaces are pressed together and the mast with this loading direction will behave less elastically as one without a fracture formation.
All previously dealt with methods have the common disadvantage that with them the condition that the mast or its anchoring with the respective loading cases may change its position in or on the ground may not be exactly taken into account. In any case it may happen that with the testing procedures it may for example arise that movements and a tilting shifting of the mast or its anchoring may occur on or in the ground and at the same time ground material is permanently displaced by the tilting of the mast or its anchoring, which of course would have an such effect on the course of the functions f that these would no longer give clear information on the stability of the mast as such.
In particular this disadvantage is to be alleviated by the invention in that a method and a testing device are put forward with which in a relatively simple and above all secure manner a sound decision and answer to the question can be achieved as to whether on the one hand a tested mast is adequately stable and whether on the other hand the obtained measuring results may point to whether a shifting of the mast or its anchoring in the ground is present, wherein even on ascertaining such shifting, information is to be made possible whether the mast is damaged or not.
From one aspect, the invention relates to a method for testing the stability of vertically anchored masts in which the mast above its anchoring is loaded with an increasing bending force F1 proceeding from a defined initial value until at the most a maximum, predetermined test force FPmax and at the same time is laterally deflected and in which the mast after completion of the loading procedure is again unloaded and with this is subjected to a restoring Force F2 reducing to zero, wherein in combination with the unloading procedure exclusively a lateral defection S2 of the mast remaining at F2=zero is ascertained and is evaluated as damage to the mast and/or its anchoring.
From another aspect, the invention relates to a method for testing the stability of vertically anchored masts in which the mast above its anchoring in a first resting procedure is loaded with an increasing bending force F1 measured from a defined initial value until at the most a maximum predetermined test force FPmax and at the same time is laterally deflected and in which the mast after completion of the loading procedure is again unloaded and with this is subjected to a restoring force F2 reducing to zero, and in which the master after the first testing procedure in the same testing plane in a second testing procedure is loaded with a second test force F3 directed oppositely to the first test force F1 and with this is laterally deflected, whereupon the mast is again unloaded and with this is subjected to a reducing restoring force F4 reducing to zero, wherein in combination with the loading procedures at least the highest reached test force FP in each case or at least a part course of the loading characteristic curve at least of the second testing procedure is determined, wherein in combination with the unloading procedures exclusively a possible lateral deflection S2, S4 of the mast remaining at F2=0 and/or F4=0 is ascertained and wherein the results of both ascertainings are evaluated as damage to the mast and/or as a damage to its anchoring.
With the solution according to the method according to the invention in a surprising and very simple manner it is possible to acquire the condition of the system mast/anchoring and also the condition of the anchoring of the mast in the ground as well as of the mast even on testing, and specifically even then when with the testing of the system the maximum testing force has not been reached. It becomes evidently recognisable whether the anchoring and/or the mast has behaved solidly or stably. With respect to the anchoring it is thus recognisable whether the anchoring has resisted all forces acting on it and accordingly has not moved or whether on reaching the maximum testing force it has also given, thus has moved and as a rule has carried out a tilting movement. Indeed there are situations in practice where it is not neccesarily recognisable on the anchoring itself and/or on the ground surroundings of the anchoring whether a tilting movement and thus a tilting shifting of the anchoring has taken place during the testing procedure. Further it is recognisable whether with the tilting shifting of the mast and its anchoring, damage to the mast is present or not. Moreover it can also be recognized whether, with the anchoring which has remained solid, damage to the mast is present or not.
An essential reason for obtaining informative results on the testing of the system mast/anchoring in the simplest case of testing according to the invention lies exclusively in the drawing up and evaluation of the remaining lateral deflection, where appropriate present, of an unloading following a loading of the mast. If it is to be found that the restoring force reduced to zero after the complete unloading of the mast leads to a permanent residual deflection, then a damage to the mast and/or a tilting shifting of the mast anchoring is present.
The method according to the invention thus with respect to the methods known up to now in a very simple and quick manner permits an increased information capability of the tested system the mast and its anchoring.
For the further increase of the information cabability with respect to the damage to the mast and its anchoring, for each testing plane two testing forces acting in opposite directions are exerted on the mast in order to determine possible remaining residual deflections after the unloading. This means that for each testing plane, e.g. a compression loading in the one direction and a tensile loading in the opposite direction is applied. With this one obtains where appropriate two permanent residual deflections. Further as an alternative at least with the second testing procedure at least partly a loading characteristic curve is determined and drawn up, and specifically its course at the beginning and end. As a further alternative also the highest testing force values are measured and used for evaluation. From a comparison of these residual deflections with the part loading characteristic curve or with the highest testing force values there results even more exact information on the damage or lack of damage to the mast and/or its anchoring, in particular on the type of damage to the mast.
The information capability of the whole test may be even further increased in that a multitude of testing planes are used, in particular when with this for each plane one tests in opposite directions.